Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751991AbWCBQIB (ORCPT ); Thu, 2 Mar 2006 11:08:01 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751993AbWCBQIB (ORCPT ); Thu, 2 Mar 2006 11:08:01 -0500 Received: from mba.ocn.ne.jp ([210.190.142.172]:216 "EHLO smtp.mba.ocn.ne.jp") by vger.kernel.org with ESMTP id S1751991AbWCBQIA (ORCPT ); Thu, 2 Mar 2006 11:08:00 -0500 Date: Fri, 03 Mar 2006 01:07:54 +0900 (JST) Message-Id: <20060303.010754.30187520.anemo@mba.ocn.ne.jp> To: johnstul@us.ibm.com Cc: paulus@samba.org, linux-kernel@vger.kernel.org Subject: Re: why do we have wall_jiffies? From: Atsushi Nemoto In-Reply-To: <1140202014.5479.4.camel@leatherman> References: <17397.25985.646489.878694@cargo.ozlabs.ibm.com> <1140202014.5479.4.camel@leatherman> X-Fingerprint: 6ACA 1623 39BD 9A94 9B1A B746 CA77 FE94 2874 D52F X-Pgp-Public-Key: http://wwwkeys.pgp.net/pks/lookup?op=get&search=0x2874D52F X-Mailer: Mew version 3.3 on Emacs 21.4 / Mule 5.0 (SAKAKI) Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1652 Lines: 37 Oh, I missed this thread... >>>>> On Fri, 17 Feb 2006 10:46:53 -0800, john stultz said: >> In other places there is code that uses (jiffies - wall_jiffies). >> However I can't see any way that jiffies and wall_jiffies could >> ever be different (except for a few nanoseconds while executing the >> code above). I also can't see any way that `ticks' could ever be >> anything other than 1. >> >> Is the wall_jiffies stuff just a leftover from days when we used to >> do timekeeping from a softirq? Or am I missing something >> fundamental? john> Its only use right now is that on some arches we increment john> jiffies when we detect lost ticks. This then forces xtime to be john> updated the appropriate number of times. Currently, jiffies and wall_jiffies is _really_ different most of time. The jiffies is almost always one bigger than wall_jiffies (at least on i386 and MIPS). Please refer my yesterday's mail (subject: jiffies_64 vs. jiffies) for the reason. john> It probably could be killed and the arches can just call john> do_timer() the appropriate number of times. That might clean john> some things up. My TOD work would also make it unnecessary. I just posted a patch to doing this (subject: [PATCH] simplify update_times ...). I thought only x86_64 is doing such thing, right? Also, I suppose then we can get rid of wall_jiffies completely. --- Atsushi Nemoto - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/